In summer 1993 while on assignment overseas, near the small town of General Crespo, Entre Rios, Argentina, an airplane with 14 people on board had radioed an emergency due to heavy smoke in the cockpit and cabin. The crew informed the control tower that they could not see anything inside the aircraft because of the smoke. Minutes later the aircraft crashed in a field killing all aboard. The following investigation determined that a battery shorted out, melted and produced dense smoke and toxic gases that spread to the interior of the aircraft.
In recent years there have been worldwide a number of smoke/fires in the cockpit and cargo compartments of airplanes, some of which have resulted in serious accidents and loss of life. Although action has already been taken to increase the safety of these compartments by improving the fire-resistance of liners, the continuing occurrence and the seriousness of the consequences of fire have resulted in a review of countermeasures to minimize its effects.
Recent investigations conducted by several fire departments in the United States of America and England focus attention on the smoke as being pivotal in the loss of life of fires in enclosed structures as it silently builds up. This invention addresses the problem of the exhaustion of smoke and gases rather than the fire itself. This invention aims to reduce the accumulation of smoke in the cockpit by siphoning out the smoke before it adversely affects the flight crew and thereby allowing additional time for landing.
From the National Transportation Safety Board files:
Douglas MD-81: Shortly after departure on Oct. 16, 1993, heavy smoke emanating from the overhead electrical panel on a Swissair McDonnell Douglas MD-81, registration HB-INH, a regularly scheduled passenger flight from Munich to Zurich. On board the airplane were 88 passengers and seven crew members. The flight-crew reported they smelled something abnormal in the cockpit approximately 10 minutes after takeoff while the airplane was at an altitude of 18000 ft. A few moments later, increasingly dense smoke became noticeable in the area of the overhead panel. The flight crew declared an emergency and returned to Munich. The "Electrical Smoke in Cockpit" checklist did not provide guidance on how to identify the origin of the smoke or how to isolate the source of the fire because the smoke was rapidly thickening. The flight-crew was unable to read and complete the checklist, since visibility became extremely limited and coordination was difficult in the cockpit The airplane was substantially damaged by smoke and overheated electrical components.
Beech 200: On Oct. 27, 1993, shortly after departing the Reno Canyon International Airport, a Beech Model 200 airplane, N191FL, sustained an electrical fire causing the cockpit and cabin to fill with smoke. The pilot reported that the smoke became progressively more intense, greatly restricting visibility in the cockpit and making breathing increasingly difficult. To facilitate removal of the smoke, he opened the cabin pressurization dump valve and the storm window. He estimated that one additional minute of in-flight operation would have resulted in incapacitation. The pilot managed to return the airplane to the airport. The landing gear collapsed on touchdown and the airplane was substantially damaged, but none of the five persons aboard was injured.
Boeing 737-217: Smoke was observed in the cabin approximately 15 minutes after takeoff. The aircraft descended to below 10,000 ft. The cabin pressure was dumped and the plane proceeded to land. The smoke dissipated after landing. Maintenance personnel found a shorted out battery.
Lockheed 1011: In 1980, in the worst commercial in-flight fire and smoke accident in Saudi Arabia, a L-1011 aircraft with 300 pilgrims plus all crew members perished from smoke inhalation inside the aircraft. There was no simple way to evacuate the smoke in the cabin and cockpit while flying.
Douglas DC-8: May 16, 1996; while cruising at 35,000 feet, the flight crew saw a spark followed by smoke in the cockpit. The flight crew donned masks and goggles and initiated an emergency descent. The flight engineer attempted to isolate the smoke, but was unable to identify the source. After landing an inspection revealed that the glareshield ballast had burned out.
Douglas DC-9: In a fairly recent air disaster, a DC-9 of ValuJet Airlines crashed in the Everglades near Miami, Fla., killing all onboard. The preliminary investigation indicated that heavy smoke in the cockpit and cabin, which the pilots had reported, appeared to be the cause of the accident.
It is appropriate at this point to mention that in critical situations of electrical smoke in the cockpit during flight the make-up and toxicity of smoke changes drastically when different materials are present in a combustible environment. In addition to obscuring vision, inhalation of toxic gases causes dizziness, confusion, disorientation, and mental and physical incapacitation of the flight-crew, making it impossible to see properly or follow emergency procedures.
These events and the common denominator of smoke and hazardous gases/fluids in airborne aircraft, drove me to conceptualize a self-operated device that by just utilizing the aircraft motion would serve to alleviate the problem and would function even in case of electrical power interruption. In other words, a system would siphon smoke, gasses and fluids in aircraft out of the cockpit, without affecting internal conditions such as pressure, temperature, oxygen, and heat.
A cost effective aircraft fire suppression system is not yet a reality. The only components in a transport category airplane having fire extinguishing devices are the engines.
Two methods of smoke evacuation were found in following patents.
U.S. Pat. No. 4,552,325 (to Bruensicke) provides a smoke evacuation system for evacuating smoke from an interior cabin of a pressurized aircraft by providing a closed smoke evacuation outlet in the skin of the aircraft in communication with a smoke disposal chute extending upwardly from the cabin's ceiling. Upon activation of the outlet, smoke will be discharged into the external airstream, with the differential pressure between the relatively high pressure in the cabin and the relatively low pressure in the external atmosphere, particularly at the high cruising altitudes associated with operation of modern transport aircraft. Operation of the smoke evacuation system depends on the differential pressure between the interior and exterior, therefore, it might not function effectively at lower altitudes. On the other hand, this system provides means for evacuating smoke from the cabin portion of the aircraft only. However, most smoke related incidents occurred in cockpits and cargo holds. In the case of the ValuJet incident (1995) the smoke was generated in the cargo compartment. The device taught by this patent would have evacuated the smoke after it has passed through the passengers' cabin. Extensive structural modifications of an airplane are required to install this system.
U.S. Pat. No. 5,312,072 (to Eklund) teaches a smoke evacuation nozzle for removing smoke from passenger cabin of an airplane. The nozzle has a converging portion located in the space between passenger cabin ceiling and fuselage pressure hull, and a diverging portion located within dorsal fin. Eklund further teaches that the nozzle maintains sonic flow at both high cruising and low descent altitudes. However, function of the evacuation still depends on the differential pressure. Additionally, using this device exhausted smoke from cockpit or cargo would also have to pass the passenger cabin before being evacuated. Furthermore, extensive structural modifications of an airplane are also required to install this system
The present invention overcomes these drawbacks and presents several advantages. It is an enduring lightweight device that will vent "in situ" the cockpits of almost any aircraft. It can be installed in a few hours without major structural modifications or disruptions. As a result, the smoke is expelled in a more direct path from the cockpit to the outside of the vessel. And most importantly its suction function does not require electrical power, and does not depend on the pressure difference between the interior air pressure and exterior environmental pressure.